The results of epidemiologícal observations made on Carríon's disease (verruga peruana) and cutaneous leishmaniasis (uta) in Huaillacayán valley (10º18' latitude South) are presented. The purpose of the study was to determine the altitude limits of the endemic zones, and the incidence of both discases in relation to thesc altitudes. The principal conclusions obtained were the following: 1 . The endemic zone of uta ranged from 900 to 3,000 meters of altitude above sea level. The upper limit of the endernic zone of Carrion's disease was also about 3,000 meters, but in this case the lower limit could not be determined, due to aplication of DDT insecticide during previous years between sea level and 780 meters. Nevertheless, the author suggests, through personal observations and technical judgement, that in the Huaillacayan valley the verruga zone probably descends more than the uta zone. 2. The incidence both of uta and verruga seems to be determined by the altitude of the localities above sea level. The highest incidence of verruga was found from 900 to 1,800 meters, while that of uta ranged from 1,800 to 2,700 meters. 3. In Huaillacayan valley the endemie zone, both of verruga and uta, descended more than in the Rimac valle, which is situated at one and a half grade south of Huaillacayan.